Java API将字符串拆分为不同长度的子字符串

Question

I have a input string of known length. I have to split this input string in 30 substrings of different lengths. For ex:-

Input string: "abcdefghijklmnopqrstuvwxyz"
Output string: "a","bcd","efgij","kl","mnopqrstu","v","wx","yz"

I wanted to know if there is some sort of API or way where I can provide the lengths, based on which I want to split the string, and get the output at one go instead of multiple steps.

Any help will be highly appreciated.

Answer 1

One way which works out of the box is using RegEx . Here's an example that splits it into 4, 3, 5, 2 and the rest of the string (the first value of the mathed groups is the entire string, that's why I started from 1):

String input = "abcdefghijklmnopqrstuvwxyz";
Matcher m = Pattern.compile("^(.{4})(.{3})(.{5})(.{2})(.*)").matcher(input);
if (m.matches()) {
    for (int i = 1; i <= m.groupCount(); i++) {
        System.out.println(m.group(i));
    }
}

however this is much slower than splitting the string using a simple for, using the dimensions given. You need to take into account speed and quality over ease of use.

More about regular expressions: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

Answer 2

No need for an API. It took just 1 minute to write a method to do that:

public static List<String> splitString(String inputString, int... lengths) {

    List<String> substrings = new ArrayList<String>();

    int start = 0;
    int end = 0;

    for(int length : lengths) {

        start = end;
        end = start + length;

        String substring  = inputString.substring(start, end);
        substrings.add(substring);
    }

    return substrings;
}

Calling splitString("abcdefghi", 3, 4, 2) will produce : [abc, defg, hi]